Even the most confident gardeners I talk to admit to some level of anxiety when it comes to pruning their perennials. Fear of “hurting the plants” typically results in doing nothing at all. And while no harm will come from NOT pruning your plants, there are many compelling reasons to do so.
I’ve already covered one important gardening task – deadheading. Today’s post is about cutting back.
I cut back my plants to delay growth, achieve a more compact and attractive shape, and avoid staking.
Late-season plants such as sedum “Autumn Joy”, chrysanthemum and Montauk daisy spend most of the summer growing. If left unpruned, by August or September they will be tall and leggy, and most likely require staking. Worse, they will often produce only a few blooms atop those too-tall stalks, resulting in an ungainly appearance.
Cutting these plants down by half (sometime in late spring) will reduce or even eliminate the need for staking – and you KNOW how much I hate staking!
Here’s a great example using one of my favorite perennials. Joe-Pye weed is a late bloomer that grows nice and tall and is reliably deer resistant. The problem is that it grows a little TOO tall – as high as 7 or 8 feet – and tends to lean heavily, with one lone bloom atop each stem. Take a look at this plant unpruned:
So sometime in June (or when the plants are about 2′ tall), I cut them all back by one third:
In a week or so they will shoot out new leaves from where I made the cuts:
This is what they look like two weeks later:
In addition to being more compact and bushy, the plants will produce several blooms, rather than just one – and again, no staking!
Other plants that are improved by cutting back are those that grow too-tall, too-fast. Where I garden we typically get long stretches of rain in spring – this sends perennials shooting up faster and taller than usual, and by the time summer comes these plants are way too tall and in desperate need of staking. Plants like nepeta and coneflower shoot up like wildfire, and while I like some height in the garden, I DON’T like skinny, stringy-looking stems. So I cut back, by about half, many of my spring and summer blooming plants when they are about 12-18” high.
Take a look at two different bee balms in my garden. This plant was installed last summer – when it grew to about 18″ this spring I cut it down by half. It’s nice and bushy, compact, and covered with blooms:
Now look at the bee balm I planted a few weeks ago:
This plant is gigantic (over 5′ tall) – leggy, spindly and pretty unattractive.
Which leads me to another great benefit to cutting back:
This is that same ugly guy from the photo above. When the flowers were finished I cut the stalks down – and look! – new leaves emerging. They probably won’t produce blooms but the plant will look fresh and clean for the rest of the season.
It’s important to note that not all plants benefit from this type of pruning – perennials such as peonies, astilbes and alliums will not respond the way I described above, and worse – you’ll lose the blooms for that season as well. A search on-line or in a gardening book will help you determine if you should prune or not.
So what are you waiting for? Sharpen up those pruners and get out there! And as always, I’m happy to answer all of your gardening questions here!